: Hematopoietic stem cell transplantation (HSCT) has revolutionized the treatment of blood disorders, yet is severely limited by issues of donor/recipient immune incompatibility. Advances in stem cell biology hint at the means of circumventing these limitations through the generation of genetically matched tissues via somatic cell nuclear reprogramming. However, significant technical and ethical impediments must first be overcome. A 5-year career development plan is described wherein the principal investigator seeks to advance the understanding of nuclear reprogramming, while establishing an academic career in HSCT. The candidate will build on training in molecular genetics and clinical hematology/oncology to develop a command of developmental and stem cell biology under the mentorship of Dr. George Q. Daley. Dr. Daley is a leader in stem cell biology, with a comprehensive research program uniquely equipped to support the proposal. The plan is ideally conducted in the Division of Hematology at Children's Hospital, Boston, given the Division's distinguished record for training physician-scientists in a rich and collaborative research environment. The research is guided by the central hypothesis that careful analysis of normal mammalian embryonic development will reveal factors that can facilitate reprogramming in vitro. The studies focus on two poorly understood events in reprogramming: DMA demethylation and the establishment of pluripotency. Using a combination of molecular, genetic and developmental analyses, we aim to determine the roles of candidate factors implicated in normal embryogenesis and reprogramming. The specific aims are to: 1) Determine if cytidine deaminases are essential for active DMA demethylation in the zygote, and whether they facilitate reprogramming during nuclear transfer, and (2) Determine if the transcription factor Nanog activates a pluripotency gene expression program during embryogenesis, and whether it can facilitate reprogramming after nuclear transfer. The aims address questions of fundamental relevance in developmental biology, with potential significance for stem cell therapy. Additionally, execution of the aims will enable the principal investigator to develop the expertise necessary to establish a specialized scientific niche, from which an academic career in HSCT can be built. (End of Abstract)